This invention relates generally to coaxial transmission line structures for the propagation of electromagnetic waves, such as microwaves, and more particularly to interconnecting a beam lead semiconductor device into such a structure. Further, this invention relates to a beam lead rod assembly utilizing a beam lead semiconductor device which allows the standardization of interconnecting such a device into a coaxial structure, such as into a gap formed in the center conductor of a coaxial structure by connecting opposite ends of the rod assembly to the end portions of the center conductor defining the gap therebetween or between the outer and the center conductor.
It is well-known that in certain microwave applications, utilizing a semiconductor device, the circuit broadband frequency response is limited by the parasitic reactances of the device package. For example, the high frequency limit of the useful frequency range of a broadband microwave detector, using a point contact diode, is usually limited by the parasitic reactances of the diode package.
While devices such as point contact diodes have performed reliably in the past, there has been developed a new and different kind of semiconductor device which is much more broadband, such as a beam lead rectifier. Parasitic reactances of a beam lead semiconductor device are usually quite low. Generally speaking, beam lead devices are semiconductor devices with beam leads that have been formed by electrodeposited gold. These leads make contact to the semiconductor chip and typically extend 10 mils, in opposite directions, from the chip. Therefore, the beam leads form the connections to the chip, eliminating the often difficult problem of making contact with the chip. Beam lead devices require very careful handling to avoid damaging the thin beam leads.
Because of their planar type construction, beam lead devices are very compatible with, and have been widely used in, microwave circuits where the circuit is etched on a planar microstrip substrate. The beam lead device can be mounted directly to the planar circuit on the substrate by thermocompression bonding.
Beam lead devices have generally been found not only to be more broadband, but to have more repeatable electric characteristics and to be more rugged than, for example, point contact diodes, and therefore are very desirable for incorporation as the active element in coaxial structures. However, beam lead semiconductor devices, including beam lead diodes, are extremely small in size and the handling of such beam lead devices must be done with great care. The leads are easily distorted or broken by the normal pressure or squeeze handling and most vacuum pencil tips are too large and the vacuum pencils may draw the diode into the vacuum system. Accordingly, it is of utmost importance that a package be found that not only allows the beam lead device to be properly mounted, but that is also compatible with standardization so that a beam lead diode may be incorporated into a coaxial structure, and that also has low parasitic reactance.
Beam lead Schottky diodes, beam lead PIN diodes, and beam lead capacitors, are typical beam lead semiconductor devices that can be used in the beam lead rod assembly of this invention. It is to be understood that the rod assembly can use any and all other type beam lead devices for a multitude of applications. One of the primary usefulnesses of the package of the present invention is the ease in which it can be incorporated into a coaxial structure.
Accordingly, one of the objects of this invention is to provide a package which may be placed in series with the center conductor of a coaxial structure and which can hold any beam lead semiconductor device.
It is a further object of this invention to provide a package for incorporation as an element into a coaxial structure, either in series or in parallel or as a termination, which is particularly applicable for housing beam lead semiconductor devices.
It is still another object of this invention to provide a convenient holder for a beam lead semiconductor device which allows for standardization of connections thereto.